#include<stdio.h>

const int N = 25;

int n;

int main()
{
    int a[N];
    scanf("%d", &n);
    int tmp;
    int cnt = 0;
    int sum = 0;
    while ((scanf("%d", &tmp)), tmp)
    {
        a[cnt] = tmp;
        sum += tmp;
        cnt++;
    }
    if (cnt < n)
    {
        printf("%.2lf", (double)sum / cnt);
    }
    else
    {
        sum = 0;
        for (int i = 0; i < n; i++)
            sum += a[i];
        printf("%.2lf", (double)sum / n);
    }
    return 0;
}